Translational profiling of macrophages infected with Leishmania donovani identifies mTOR- and eIF4A-sensitive immune-related transcripts

Abstract

The protozoan parasite Leishmania donovani (L. donovani) causes visceral leishmaniasis, a chronic infection which is fatal when untreated. Herein, we investigated whether in addition to altering transcription, L. donovani modulates host mRNA translation to establish a successful infection. Polysome-profiling revealed that one third of protein-coding mRNAs expressed in primary mouse macrophages are differentially translated upon infection with L. donovani promastigotes or amastigotes. Gene ontology analysis identified key biological processes enriched for translationally regulated mRNAs and were predicted to be either activated (e.g. chromatin remodeling and RNA metabolism) or inhibited (e.g. intracellular trafficking and antigen presentation) upon infection. Mechanistic in silico and biochemical analyses showed selective activation mTOR-and eIF4A-dependent mRNA translation, including transcripts encoding central regulators of mRNA turnover and inflammation (i.e. PABPC1, EIF2AK2, and TGF-β). L. donovani survival within macrophages was favored under mTOR inhibition but was dampened by pharmacological blockade of eIF4A. Overall, this study uncovers a vast yet selective reprogramming of the host cell translational landscape early during L. donovani infection, and suggests that some of these changes are involved in host defense mechanisms while others are part of parasite-driven survival strategies. Further in vitro and in vivo investigation will shed light on the contribution of mTORand eIF4A-dependent translational programs to the outcome of visceral leishmaniasis.

Infection by the Protozoan Parasite Toxoplasma gondii Inhibits Host MNK1/2-eIF4E Axis to Promote Its Survival

“…Bone marrow-derived macrophages (BMDMs) were generated from 6 to 8 week-old female C57BL/6 mice (Jackson Laboratory), as previously described (Leroux et al, 2018 ; Zakaria et al, 2018 ; Chaparro et al, 2020 ). Briefly, marrow was extracted from bones of the hind legs, red blood cells were lysed, and progenitor cells were resuspended in BMDM culture medium supplemented with 15% L929 fibroblast-conditioned culture medium (LCCM).…”

“…Changes in translational efficiency represent a fundamental mechanism in normal biological processes including cell differentiation, growth, metabolism, and proliferation (Gebauer and Hentze, 2004 ; Hershey et al, 2012 ). Translational control is also required for balanced immune functions (Piccirillo et al, 2014 ) and is observed during infectious diseases (Alain et al, 2010 ; Mohr and Sonenberg, 2012 ; Walsh et al, 2013 ; Nehdi et al, 2014 ; Leroux et al, 2018 ; Hoang et al, 2019 ; Chaparro et al, 2020 ). In eukaryotic cells, translational efficiency is mainly regulated at the initiation step during which ribosomes are recruited to the mRNA, a process facilitated by recognition of the mRNA 5′-m 7 G-cap structure by eukaryotic initiation factor 4E (eIF4E), which, together with scaffold protein eIF4G and RNA helicase eIF4A, form the eIF4F complex (Jackson et al, 2010 ).…”

The host mTOR pathway and parasitic diseases pathogenesis

“…Regarding “in vitro” studies, macrophages infected by Leishmania parasites show alteration of its proteome (Hassani and Olivier 2013 ). The results of several “in vitro” proteomic studies on infected macrophages indicated that leishmanial-glycoprotein 63 (GP63) cleaves mTOR and inhibits (inactivates) the production of the mTORC1 (Chaparro et al 2020 ; Matte and Descoteaux 2011 ; Shapira and Zinoviev 2011 ; Shertz and Cardenas 2011 ). The degradation of important components of the Akt/mTOR axis, containing mTOR, Akt, and the tuberous sclerosis complex-2 (TSC-2) has been implicated in that process (Matte and Descoteaux 2011 ).…”

“…Another study investigated the role of Leishmania parasites in the alteration of host mRNA translation in favor of the infection. Such translational modifications mostly target central cellular functions by overexpressing proteins involved in RNA metabolism and chromatin remodeling and by inhibiting the expression of proteins relevant to antigen presentation and intracellular trafficking (Chaparro et al 2020 ). In silico analyses related to such a discovery identified poly (A)-binding protein cytoplasmic 1 (PABPC1) via mTOR-activated translation and growth factor-beta (TGF-β) through activated translation depending on RNA helicase eIF4A during leishmaniasis infection.…”

Channeling macrophage polarization via selective translation inhibition by rocaglates increases macrophage resistance to Mycobacterium tuberculosis

“…This property of rocaglates may be particularly important for directing macrophage polarization when the receptor signaling is disrupted by mutations, microbial factors or negative biological regulators.The above data suggest that rocaglates may represent a novel class of HDTs with broad applications in vivo. Rocaglates are active against protozoan infections, such as malaria(57) and visceral leishmaniasis(58).…”